1. Field of the Invention
The present invention is directed to systems and methods for monitoring the health and status of an aircraft, via sensors, and more particularly to energy conserving methods and systems for sensor systems used to evaluate the health and status of the aircraft.
2. Description of the Related Art
A typical aircraft sensing system includes a processor (e.g., a microcontroller), a memory, a sensing element, and a power source. The power source can either be dependent, e.g., from an aircraft power bus, or independent, e.g., a battery. Design of the aircraft sensing system using independent power sources offers an advantage of monitoring events that occur when aircraft power is not on, e.g., towing operations. Still further, independent power sources offer potential weight saving advantage due to the removal of electrical wiring, e.g., power and data transmission wiring. However, this weight saving advantage must be balanced against factors such as a weight of the power source and requisite performance characteristics of the sensors, e.g., the amount of time the sensor is operational and the acuteness of sensor data. Typically, greater performance characteristics, e.g., longer operation times and more acute sensor data, require the sensor to operate at a higher energy state and, thus, draw more power. In fact, continuous operation of the sensor may require a significant power draw, limiting the useful battery life. If the battery is depleted and the system stops operating before measuring the data associated with a particular event, the event will go undetected.
Conventional techniques for conserving energy in aircraft sensing systems having an independent power source are often designed to operate in a sleep mode until sensing are required. According to these techniques, the sleep mode can be accomplished using a timer. The timer-based sleep mode turns off the sensing system during the sleep mode, and turns on the sensing system during a wake mode after a predetermined amount of time has passed. During the sleep mode, the processor is configured to store the current state of registers and/or memory, and cease all other activity, such as data collection. A timer periodically wakes the sensing system to measure a desired value, generate sensor data, transmit the sensor data, and enter the sleep mode again. The fraction of time the sensor is in a wake state is typically referred to as a duty cycle. In order for the energy use of the system to be low, the duty cycle needs to be very low, e.g., the sensing system remains in the sleep mode for a larger period of time in relation to the wake mode. However, this timer-based sensing system loses situational awareness during sleep mode since, during sleep mode, the sensing system is inactive and, accordingly, the system does not collect nor provide sensor data. Moreover, while in sleep mode, these sensors fail to monitor potentially dangerous and detrimental aircraft events, e.g., dramatic changes in pressure, temperature, vibration and strain. Ultimately, this can lead to unsafe aircraft conditions since the timer-based sensing system remains unavailable until the timer wakes the sensing system at predetermined times.
Therefore, there is a need for an aircraft sensing system that conserves energy, yet preserves situational awareness and continuously monitors for potentially dangerous and detrimental aircraft events.